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Biomedical subjects

B C Johnson

Publications and source records attributed to B C Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1987

Crucial dietary factors in maximizing life span and longevity in autoimmune-prone mice.

When the energy intake of (NZB X NZW)F1 female mice was reduced to 60% of the intake of simultaneously ad libitum-fed mice, the early death associated with autoimmune-based renal disease in this strain was greatly delayed. The length of prolongation of disease-free life depended not only on the decreased energy intake but also on the energy source. In the group of mice with 60% intake of a carbohydrate-free (i.e., high fat) diet, mean longevity was doubled as compared to that of ad libitum-fed mice. However, when the nonprotein energy was supplied by carbohydrate (sucrose and glycerol) the mean longevity was three times that of the ad libitum-fed groups, although survival times varied widely. With ad libitum feeding the nonprotein energy source did not significantly affect longevity. Clearly, although energy intake restriction provides significant influence on longevity, very high fat diets do not give the same protection as do high carbohydrate diets. The basis for this difference is not entirely clear and several explanations are possible.

Animals↗
PubMed1987

Influence of extremes of protein and energy intake on survival of B/W mice.

Energy restriction increases longevity and life span of B/W mice as it does in mice of other long-lived or short-lived strains. Mice of autoimmune-prone strains that develop certain diseases of aging experience an increase in median longevity when energy intake is restricted early in life. The present experiments analyze the influence of restricting energy intake while feeding constant, adequate and greatly excessive amounts of protein, and constant amounts of minerals and vitamins. The experiments assess the influence of excess protein intake in mice fed ad libitum versus those restricted in energy intake. Ad libitum feeding of diets with protein composition ranging from 15 to 50% did not alter longevity or onset and manifestations of renal disease in B/W mice. In mice consuming a restricted energy intake of a diet providing identical amounts of protein to those consumed by ad libitum-fed mice, whether the protein intake was very high or normal, longevity was equally greatly prolonged. Ad libitum feeding of diets of greatly differing protein content is well tolerated by B/W mice. Both the 15 and 50% protein diets, when ad libitum fed, permitted expression of autoimmune disease and glomerulonephritis in B/W mice but did not adversely influence development or progression of disease. Restriction of energy intake of either the normal protein diet or the high protein diet greatly prolonged the life of mice of the autoimmune-prone, glomerulonephritis-prone B/W strain.

Animals↗
PubMed1987

Understanding the relational impact of the health care marketing exchange: a review of the social implications of therapeutic communicator style.

Though the benefits derived from verbal communication between practitioner and patient often are beyond the control of most health care marketers, this encounter includes nearly all of the personality and social appeals that are critical to the development of a successful and long-lasting marketing exchange. To enable marketers of health care to understand more fully the communication context in which practitioners operate, the author reviews the social implications of therapeutic communicator style.

Communication↗
PubMed1986

Calories versus protein in onset of renal disease in NZB x NZW mice.

Autoimmunity-prone (NZB x NZW)F1 (B/W) female mice are used as a model of human lupus erythematosus. When full-fed, these mice die of glomerulonephritis between 7 and 11 (average 9) months of age. When food intake is restricted to 60% of calories, the onset of this disease is delayed and the mice live greatly prolonged lives free of disease. Since high protein intake is commonly associated with acceleration of kidney damage in humans and experimental animals, the current experiments were designed to employ diets in which protein concentration was as high as possible. The observations demonstrate clearly that with this model of autoimmune disease, total calorie intake (from whatever source) exerts an overriding influence on life span. A higher calorie intake leads to early death and restricted-calorie intake leads to an increased life span. When B/W mice are full-fed, with respect to calories, feeding diets of greatly differing protein composition did not influence life span significantly. By contrast, calorie restriction of diets, even of very high protein content or of lower protein content, greatly prolonged life of B/W mice. Even with exceedingly high protein intake (greater than 83% of the calories) it is not protein per se but the total calorie intake that exerts the greatest influence that determines length of life in mice of this autoimmunity- and glomerulonephritis-prone strain.

Animals↗
PubMed1984

Cross-reacting material to monoclonal anti-G6PD in the absence of catalytic activity.

Monoclonal antibody prepared against highly purified rat liver G6PD was used to probe the mode of regulation of this enzyme in a mammalian model system. Material cross-reacting with antibody against liver G6PD was found in similar amounts in extracts of two genetically related rat hepatoma cell lines, only one of which exhibits detectable enzymatic activity when both are cultured under identical conditions in vitro. The data suggest a post-translational event is necessary for the expression of catalytic activity for G6PD in this model system.

Animals↗
PubMed1984

Calorie source, calorie restriction, immunity and aging of (NZB/NZW)F1 mice.

It is frequently stated that high fat diets are harmful with respect to nutrition and disease development. Herein, (NZB/NZW)F1 autoimmune-prone mice were compared under the influence of different calorie intakes and different calorie sources. Decreased calorie intake prolonged life and delayed onset of glomerulonephritis. This influence of restriction of energy intake was greater than any influences of dietary energy source. Parameters affected strictly by restricted calorie intake were: 1) longevity, 2) delayed onset of glomerulonephritis, 3) greatly decreased circulating immune complexes, 4) decreased production of anti-DNA antibodies, 5) increased thymocyte proliferation in response to exogenous Interleukin-2 (IL-2), 6) increased IL-2 production by spleen cells stimulated by concanavalin A and 7) marked increase of mixed lymphocyte reaction of spleen cells. Parameters affected both by restriction of calorie intake and by high sucrose content in full-fed mice and not obviously related to longevity and protection from glomerulonephritis were: 1) plaque-forming cell response to sheep red blood cells in vitro and 2) cytotoxic cell-mediated immune response generated by in vitro exposure to allogenic antigen.

Aging↗
PubMed1984

Comparison of fetal and adult retinol and retinoic acid binding proteins in bovine serum and pigment epithelium.

Cellular retinol binding protein (CRBP) and cellular retinoic acid binding protein (CRABP) were assayed in bovine eye pigment epithelium (PE) cytosol from both early fetal and young adult animals. Both fetal and adult PE contain CRBP but only fetal PE contains CRABP. Blood retinol binding protein (RBP) was also assayed in serum from fetal and adult animals. Both fetal and adult serum contain RBP. A novel albumin adsorption technique (Affi-Gel Blue) combined with refinements of the sucrose gradient centrifugation technique provide a better assay method for retinoid receptors than polyacrylamide disc gel electrophoresis. Our findings support the hypothesis that retinoid receptors may cause or be the consequence of differentiation in animal tissues.

Adsorption↗
PubMed1982

Preparation of a monoclonal antibody to rat liver glucose-6-phosphate dehydrogenase and the study of its immunoreactivity with native and inactivated enzyme.

A monoclonal antibody of the IgG class was prepared against rat liver glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) by the hybridoma technique. This antibody does not affect the catalytic activity of the enzyme and shows crossreactivity with the palmitoyl CoA-inactivated G6PD. By solid phase radioimmunoassay, the presence of crossreacting materials in comparable amounts was determined in liver homogenate supernatants from rats that had been starved and refed a high-sucrose diet (containing a high level of G6PD activity) and from rats that had been starved and refed a high-fat diet (containing a low level of G6PD activity). These findings indicate that G6PD is present in an inactive form in rats fed a high-fat diet. The monoclonal antibody will facilitate isolation and characterization of the inactive variant G6PD.

Animals↗
PubMed1981

Post-translational carboxylation of preprothrombin.

In summary, in this review on the function of vitamin K in post-translational modification of precursor proteins by carboxylation of certain glutamyl residues, I have tried to cover in particular the recent work on the reaction, the enzymes involved and the mechanisms being considered. In doing this I have also considered vitamin K, its discovery, its functional form and the possible relation of its metabolism to the carboxylation reaction. Equally the various vitamin K-dependent gla-containing proteins currently known have been described. The carboxylation of synthetic small molecule exogenous substrates and the synthesis and metabolism of the products of carboxylation are of great help in studying the reaction. Structural specificity of vitamin K analogs in vivo and in vitro has been compared and the use of various antagonists in vivo and in vitro considered in attempts to gain an understanding of the overall reaction. The reactions subsequent to carboxylation, e.g., the activation of prothrombin to thrombin via serine proteases and the related activation of the other vitamin K-dependent proteins have not been considered in this review. The review has not covered prothrombin or other vitamin K-dependent protein isolation, nor the determination of these proteins. As the vitamin K-dependent protein carboxylation story has developed over the past six years, a number of reviews have been written which help in keeping up with the various aspects of the field as it has expanded. These reviews refer to many of the papers I have had to eliminate due to space limitations. They are referenced as 469-489. The review is in no sense comprehensive and many papers have been missed or only mentioned. I have tried to concentrate on the more recent work and, thus, much of the very fine work of the 1940's on vitamin K chemistry is hardly mentioned. Some redundancy has been built into the organization of the review so that a reader can obtain a reasonable view of any one section without having to search the whole review for all possible relevant information on any particular part of the field.

Animals↗
PubMed1981

Pair-feeding in the dietary control of glucose-6-phosphate dehydrogenase.

The great increase ("overshoot") in glucose-6-phosphate dehydrogenase activity in liver cytoplasm which follows the transfer of rats from starvation to a high sucrose diet has been recognized for a number of years. Also the fact that transferring fed rats to the high sucrose diet results only in a small increase in G6PD activity while transfer of "starved" rats to the high sucrose diet results in a 10 to 20-fold ("overshoot") increase in G6PD activity is equally recognized. This report demonstrates that the "overshoot" following 4 days without food is not due to an increase in food intake compared to the food intake of fed rats since pair-feeding during this refeeding at three different levels does not eliminate the effect of the prior fast.

Animals↗
PubMed1980

alpha-Amanitin-resistant RNA polymerase II from carpophores of Amanita species accumulating amatoxins.

DNA-dependent RNA polymerase activities have been partially purified from carpophores of the amanitin (amatoxin)-accumulating species Amanita hygroscopica and Amanita suballiacea and the non-accumulating species Amanita brunnescens and Amanita alliacea. RNA polymerase II activities purified by ion-exchange chromatography were characterized with respect to ionic strength, template, and divalent metal ion requirements and sensitivities to inhibition by alpha-amanitin. The Ki values of alpha-amanitin for RNA polymerase II activities were: 2.0 . 10(-3) M for A. hygroscopica; 3.3 . 10(-3) M for A. suballiacea; 9.8 . 10(-6) M for A. brunnescens; 10.0 . 10(-6) M for A. alliacea. Further purification with DNA affinity chromatography of activities from A. suballiacea and A. brunnescens did not alter the apparent dissociation constants of alpha-amanitin from either enzyme. The correlation between amanitin sensitivity of RNA polymerase II and the quantity of amatoxins found in carpophores suggests these peptides may play a role in regulating transcription of messenger RNA during carpophore development.

Agaricales↗
PubMed1980

Fractionation and reconstitution of vitamin K-dependent carboxylation activity in rat liver microsomes.

Attempts to purify the vitamin K-dependent carboxylation system from rat liver microsomes have not yet met with success. Purification procedures result in low yields of activity even after relatively mild separation methods. We have been able to demonstrate that one reason for these failures is that there are at least two components (which can be separated) necessary for the reaction. Recombination of the separated components is possible if the detergent (Triton X-100) concentration is lowered and ethylene glycol is added to the system. Under these conditions, vitamin K-dependent carboxylation of synthetic pentapeptide (Phe-Leu-Glu-Glu-Leu) can be totally reconstituted.

Animals↗
PubMed1980

Regulation of vitamin K-dependent carboxylation.

Vitamin K-dependent carboxylation activity measured with pentapeptide substrate (Phe-Leu-Glu-Glu-Leu) gradually decreases upon in vivo injection of vitamin K to vitamin K-deficient rats. A decrease in pentapeptide carboxylation can also be observed by the in vitro addition of antibodies against prothrombin and other vitamin K-dependent proteins to the soluble system derived from vitamin K-deficient rat liver microsomes. In both cases, adding back in vitro partially decarboxylated vitamin K-dependent proteins or purified hepatic prothrombin precursor restores the level of pentapeptide carboxylation. After warfarin treatment, a 3-fold increase in carboxylation results, which can be abolished by giving cycloheximide along with the warfarin. However, the resulting decreased activity is restored by the in vitro addition of partially decarboxylated vitamin K-dependent proteins. These data are consistent with the hypothesis that (after warfarin treatment) increased peptide carboxylation is primarily due to activation of the system by precursor proteins, rather than synthesis of an increased amount of enzyme.

Animals↗
PubMed1979

Purification of a new high activity form of glucose-6-phosphate dehydrogenase from rat liver and the effect of enzyme inactivation on its immunochemical reactivity.

A new form of cytoplasmic glucose-6-phosphate dehydrogenase (E.C.1.1.1.49) was purified from rat liver by protamine sulfate precipitation, ammonium sulfate fractionation, ion exchange chromatography with diethylaminoethyl cellulose, and affinity chromatography with Cibacron blue agarose and NADP agarose. This form of the enzyme has a specific activity of over 600 units/mg of protein and gives essentially a single band by polyacrylamide gel electrophoresis. The form of the enzyme isolated by this purification method is 3 times more active than the form purified from liver by previously reported procedures. The relative mass of this pure glucose-6-phosphate dehydrogenase enzyme was determined by disc gel electrophoresis to be 269,000. This high activity glucose-6-phosphate dehydrogenase enzyme, after inactivation by reaction with palmityl-CoA, was no longer precipitated by specific rabbit and goat antisera to this purified enzyme. Thus, the possibility still exists that starved fat-refed animals contain glucose-6-phosphate dehydrogenase (G6PD) enzyme protein in an inactivated form no longer detectable by either enzyme activity or immunoprecipitation.

Animals↗